The Bering Strait theory proposes that the first humans to reach the Americas walked from Asia across a vast stretch of land that once connected Siberia to Alaska. During the last ice age, so much of Earth’s water was locked in glaciers that sea levels dropped roughly 130 meters (425 feet) below where they are today, exposing a flat, treeless landmass between the two continents. This exposed land, known as Beringia, existed between approximately 36,000 and 11,000 years ago. For decades, this was considered the sole explanation for how people arrived in North and South America, but recent discoveries have complicated the picture significantly.
What Beringia Actually Looked Like
Beringia was not a narrow bridge. It was a broad, habitable landscape stretching from the Yukon Territory in Canada westward into eastern Siberia. The climate was too cold for trees, so the terrain consisted of dry, steppe-like grasslands sometimes called the “mammoth steppe.” The soils were warmer and more fertile than what exists in the region today, and the grasses supported a remarkable density of large animals.
Woolly mammoths, mastodons, steppe bison, horses (smaller than modern breeds), woolly rhinos, lions, and short-faced bears all roamed Beringia. Muskox, caribou, mountain sheep, brown bears, and wolves lived there too. Humans, however, were latecomers to the eastern portion of this landscape, likely not arriving in what is now Alaska until around 14,000 years ago, when warming temperatures allowed shrubs to grow and woody-plant-dependent species like moose and elk to move in alongside them.
The Clovis-First Model
For much of the 20th century, the dominant version of the Bering Strait theory was called “Clovis First.” It held that the earliest Americans were the Clovis people, identified by a distinctive style of fluted stone spear point found across North America. Clovis sites, including locations in South Dakota, Colorado, Oklahoma, Pennsylvania, Montana, and Virginia, have been dated to between 13,050 and 12,750 years ago. Under this model, people crossed Beringia, then traveled south through an ice-free corridor that opened between two massive ice sheets covering Canada: the Cordilleran ice sheet along the Pacific coast and the Laurentide ice sheet farther inland.
The problem is timing. Research published in the Proceedings of the National Academy of Sciences dated the final opening of that ice-free corridor to about 13,800 years ago, and the corridor didn’t become biologically viable, meaning it had enough plants and animals to actually sustain travelers, until roughly 12,600 years ago. That’s too late to explain even the Clovis sites, let alone earlier ones.
Pre-Clovis Sites That Changed the Timeline
The Clovis-First model began to unravel with the acceptance of Monte Verde, an archaeological site in southern Chile dated to about 14,500 years ago. People were living at the southern tip of South America a full 700 years before the inland ice-free corridor was even passable. That geographic distance alone implies they had arrived in the Americas much earlier and taken a different route.
Then came the White Sands footprints. In 2021, researchers reported fossilized human footprints at White Sands National Park in New Mexico dating to between 23,000 and 21,000 years ago. The finding was initially controversial because it relied on radiocarbon dating of seeds from a single aquatic plant species. But follow-up studies using independent dating methods confirmed the original timeline. The results, published in Science in 2023, reaffirmed that humans were present in North America during the Last Glacial Maximum itself, thousands of years earlier than any previous model predicted. These people were living well south of the ice sheets at a time when Beringia was fully exposed but massive glaciers blocked the interior route south.
The Coastal Migration Alternative
If the inland corridor was blocked by ice, how did people get south? The leading alternative is the coastal migration theory, sometimes called the “Kelp Highway” hypothesis. By about 16,000 years ago, the North Pacific coast offered a continuous, sea-level route from northeast Asia into the Americas. Rising seas early in the postglacial period had created a highly convoluted, island-rich coastline along Beringia’s southern shore, conditions well suited to people who lived off the sea.
Kelp forests, which thrive in cool nearshore waters along rocky coasts, are among the most productive ecosystems on Earth. They support dense populations of shellfish, fish, marine mammals, seabirds, and edible seaweeds. Critically, similar kelp forest ecosystems line the entire Pacific Rim from Japan to Baja California, meaning coastal migrants would not have needed to dramatically change their way of life as they moved. The kelp forests also reduce wave energy and provide natural holdfasts where boats can be secured. Along with terrestrial resources on nearby land, these habitats could have sustained migrating groups with minimal adaptation.
The major challenge for this hypothesis is evidence. Ancient coastlines are now submerged under meters of water, making archaeological sites from a coastal migration extremely difficult to find.
What Genetics Reveal
DNA evidence strongly supports an Asian origin for Indigenous peoples of the Americas, even as it complicates the specifics. Haplogroup Q, a genetic marker passed through the male line, is found in most Indigenous American populations and is also present at high frequencies in Siberian groups: 93.8% of the Ket people and 66.4% of the Selkup people of Siberia carry it. Mitochondrial DNA passed through the maternal line tells a similar story, with shared haplogroups linking the two populations.
One interesting wrinkle involves a genetic marker called haplogroup X, which appears in some North American Indigenous populations and among the Altai people of southern central Siberia but is absent from eastern Siberia. This distribution suggests the ancestral population may have come from a broader geographic region than a simple “walk across the land bridge” model would predict, and that the migration story may involve multiple waves of people from different source populations over thousands of years.
How the Theory Stands Today
The core idea behind the Bering Strait theory, that the first Americans came from Asia, remains well supported by genetics, archaeology, and geology. What has changed dramatically is the timeline and the route. The old model of a single migration across the land bridge and down through an inland corridor around 13,000 years ago no longer fits the evidence. People were in the Americas by at least 23,000 years ago, and possibly earlier. They likely used multiple routes at different times: some may have followed the coast by boat, others may have walked across Beringia when conditions allowed, and later groups may have used the inland corridor once it opened.
The land bridge itself was submerged by rising seas around 11,000 years ago, cutting the connection between the continents for good. What was once presented as a single event, a walk across a bridge, now looks more like a complex process spanning thousands of years, involving maritime technology, multiple entry points, and a timeline that keeps getting pushed further into the past as new evidence surfaces.